Weyer's De praestigiis daemonum (1563 and later editions) is universally considered in the literature on the Renaissance and on Witchcraft as the first important contribution to a rational criticism of the belief in the lore of witchcraft and in the repressive and cruel attitude toward alleged witches on the part of ecclesiastic and civil authorities. Weyer (1515-1588) for almost thirty years served as court physician to Duke William of Julich, Cleve and Berg. The atmosphere of this duchy was unusually tolerant toward both Catholics and Protestants in an epoch of terrible religious conflicts and wars. Weyer, a skillful and unbiased man, had direct contact with a number of cases of witchcraft and served as consultant in difficult situations. Out of his experience and of his unusual grasp of classical, Christian and contemporary literature came the De praestigiis daemonum which went through five editions (as well as German and French translations) during his lifetime. The book deals with witchcraft from four viewpoints--theological, philosophical, medical, and legal. It is divided into six parts, dealing with the devil, the satanic magicians, the witches, the possessed, the help for the possessed, bewitched and poisoned, and the punishment for sorcerers, witches, and poisonmongers. Weyer's book was obviously held in esteem by many of his contemporaries, as shown by the various editions and translations; but, then, it fell into oblivion with the rise of rationalism (and disbelief in the power of the devil) and of modern scientific medicine. The need for a critical English translation has become evident. With the help of a team of specialists and of a grant from the National Library of Medicine, a translation was prepared of the 1583 edition (the latest in Weyer's lifetime), complete with many references and explanatory notes, and an introduction. "Medieval and Renaissance Texts and Studies" of the State University at Binghamton has accepted the manuscript for publication. It is expected that the book will have a wide appeal to several audiences, in particular people interested in: the history of medicine, especially psychiatry; folklore; witchcraft and its history social history; literature; religion; feminist studies.